While a driver's license does normally fill that role, it's not mandated and not everyone has a driver's license (or even a state issued ID).
Some stuff like voting you can use something like a utility bill. Some stuff will want your birth certificate. Some stuff will want multiple types of documents.
Americans have historically been against mandated government IDs (though mostly with the concept of a federal/national ID).
This whole thread is going to motte & bailey between the various forms of US gov ID. Between the union of {SSN, birth cert, driver's license (or ID in lieu thereof)}, it seems to be there's the equivalent of a federal ID. Just, like everything else we do, a terrible incomprehensible mess to Europeans.
My employer requires an SSN when I start a job. TSA keeps alleging they're going to require Real ID any day now. Voting, if I have my jurisdiction's requirements right, requires an SSN, though most people will experience that in the form of driver's license, since getting a license is usually automatic voter registration where I've lived.
Some stuff like voting you can use something like a utility bill. Some stuff will want your birth certificate. Some stuff will want multiple types of documents.
Americans have historically been against mandated government IDs (though mostly with the concept of a federal/national ID).